A digital signal isolator is a device or circuit for transmitting logic signals across a DC isolation barrier. A digital signal isolator may use optical or magnetic isolation to transmit an input signal from one side of the isolation barrier to the other. Each side of the isolation barrier may operate at different voltages, have different supply voltages and have separate, isolated ground reference voltages.
FIG. 1 illustrates a single-bit digital signal isolator manufactured by Analog Devices, Incorporated. The isolator includes edge detection circuits 101 and 103 for detecting rising and falling edges in the input signal. Edge detection circuit 101 outputs two pulses when a rising edge is detected and edge detection circuit 103 outputs a single pulse when a falling edge is detected. The output of the edge detection circuits 101 and 103 is input into an OR gate 104. The combined signals are then transferred across a micro-transformer 105. A receiver 106 then reconstructs the input signal by determining if the received signal has two pulses or one pulse.
Many applications require multi-bit communications across an isolation barrier. These needs can be accommodated by replicating the single bit isolator for as many bits as are needed. FIG. 2 illustrates a system in which three separate single-bit isolator systems 210-230 are used. Such solutions have disadvantages, however, as each single-bit isolator has its own isolation device and therefore consumes a significant amount of space on an integrated circuit. Moreover, replicating the isolators for multi-bit communication requires a corresponding increase in power consumed by the isolator system.
Accordingly, there is a need for a multi-bit isolator system and method which reduces the overall footprint of the system on an integrated circuit and which reduces the amount of power consumed by the multi-bit isolator system.